Automatic transmission fluid



United States Patent M 3,156,652 AUTOMATIC TRANSMISSION FLUID Edward G. Foehr, San Rafael, Calif, assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Filed Sept. 29, 1961, Ser. No. 141,645 5 Claims. (Cl. 252-75) This invention relates to power transmission fluids. Specifically, this invention concerns transmission fluids containing N-acylsarcosines which give improved friction control characteristics in automatic power transmission systems.

Fluids for use in automatic power transmissions must be carefully designed to meet a variety of requirements. The majority of types of automatic transmissions contain planetary'gears which are actuated by vertical metal disks, known as driven disks, which are alternated with vertically spaced driving disks. The driving disks are faced with hard fibrous material, such as brake band material or compressed composition paper. All are immersed in a suitable transmission fluid. During the driving operation the fiber faced disks and the plain metal disks come intermittently into clutching contact with each other, and thus aifect change in gear ratios corresponding to the various driving velocities. A transmission fluid is not fully satisfactory if it allows disks to grab or stick and then slip with perceptible vibration of the transmission. This phenomenon is called squawking or chattering. If, however, the transmission fluid is too oily the disks will slip upon clutching causing excessive engine speeds or flaring which in turn cause an automatic upshift of gears and a jerking motion of the car.

Prior art friction control agents have in some instances consisted of compositions obtained by reaction of unsaturated compounds with elemental sulfur. These compounds generally have been unsatisfactory, since they have a detrimental effect upon the other types of additives which may be present in the transmission fluid. Other known prior art friction control additives have decomposed or lost their friction control properties within a short time.

It has now been discovered that N-acylsarcosines possess outstanding properties which are considered desirable for friction control in modern automatic power transmissions. When added to an automatic transmission base fluid they eliminate both squawk (or chattering) and flaring in the automatic power transmissions.

The N-acylsarcosine derivatives of the present invention are illustrated by the empirical formula:

wherein R represents the hydrocarbon group of an aliphatic carboxylic acid of about from 12 to 24 carbon atoms in the carboxylic acid residue. Saturated and unsaturated acyl groups of 12 to 20 carbon atoms are preferred. These include, among others, the acyl groups of dodecene, tridecene, tetradecene, pentadecene, hexadecene, heptadecenes, octaand nonadecene moiety, as well as the eicosenoic homologues and the corresponding alkanoic acids. Acyl groups derived from acids such as laun'c, palrnitoleic and oleic are included. Acyl groups derived from oleic acid are preferred.

In accordance with this invention power transmission fluids are provided having a viscosity within the range from about 75 to 1000 SSU at 100 F. and from about 35 to 750 SSU at 210 F. The base oils are light lubricating oils and ordinarily have a viscosity of about 50 to .400 SSU at 100 F. The base oil is a lubricating oil fraction of petroleum either naphthenic or paraffinic base, un-

3,156,652 Patented Nov. 10, 1954 refined, acid refined or solvent refined as required in the particular lubricating need. Synthetic oils may also be used as base stock.

In the exemplification of compositions according to the invention, three base oils are used in preparing the blended base fluids. Base oil A is a blend of California paraflinic and naphthenic oils having a viscosity at 100 F. of 107.6 SSU and a viscosity at 210 F. of 39.7 SSU. Base oil B is a blend of Mid-Continent paraflinic and California naphthenic oils having a viscosity at 100 F. of 109.0 SSU and a viscosity at 210 F. of 39.8 SSU. Base oil C is a blend of California paraflinic and naphthenic oils having a viscosity at 100 F. of 94.0 SSU and a viscosity at 210 F. of 39.0 SSU.

The-typical supplementary additives used in these fluids for the purpose of illustration have the following chemical compositions:

CONSTITUENT R Mixed oil-soluble polymerized alkyl methacrylates having an average of 12 carbon atoms in the alkyl chain and a molecular weight of about 220,000.

CONSTITUENT S Oil-soluble copolymer comprised of monomeric constituents of alkyl methacrylate and vinyl pyrrolidone having a molecular weight of about 220,000 having mixed higher alkyl radicals in the alkyl chain.

CONSTITUENT U Oil-soluble mixture of: (1) condensate of chlorinated paraflin wax and naphthalene having a molecular weight of 1500-3000, and (2) polymerized alkyl fumarate having 12-14 carbon atoms in the alkyl groups and a molecular weight of about 3000-8000. The ratio of the two components of the mixture is 1:1.

CONSTITUENT T Oil-soluble polyisobutylene having a molecular weight of about 220,000.

CONSTITUENT K Oil-soluble basic calcium petroleum sulfonate having a ratio of basic to neutral calcium of about 7 3:1, and molecular weight of about 400.

CONSTITUENT N pour point of the fluid. Constituent K is basic and neutralizes acids formed in base fluid. Di-terbbutyl-pmresol and phenyl-ot-naphthylamine are oxidation inhibitors. The dimethylsilicone polymer is a foam inhibitor.

The following listed compositions illustrate the finished automatic transmission fluids in which the compounded base fluids are:

(D) Oil A containing Dimethylsilicone polymer do 0001 3 (E) Oil B containing- Constituent K, millimoles per kilogram 53.0 Constituent N percent 2.0 Constituent T do 4.75 Di-tert-butyl-p-cresol do 0.4 Constituent U do 0.2 Dimethylsilicone polymer do 0.001 (F) Oil C containing Constituent K, millimoles per kilogram 58.5 Constituent S percent 3.0 Constituent T do 3.6 Di-tert-butyl-p-cresol do 0.4 Dimethylsilicone polymer do 0.001 (G) Oil B containing- Constituent K, millimoles per kilogram 105.0 Constituent T percent 6.2 Constituent R do 1.0 Di-tert-butyl-p-cresol do 0.3 Phenyl-u-naphthylamine do 0.2 Constituent U do.. 0.2 Dimethylsilicone polymer do 0.001

The particular additives and the base oil can be combined in a variety of Weight ratios with respect to each other. For instance, the ratio of Constituent K may vary from to 250 millimoles per kilogram of the base oil; Constituent N and Constituent S may vary from 1.0 to by weight of base oil; Constituent T may vary from 1.0 to 15% by weight of base oil; Constituent U may vary from 0.1 to 1.0% by weight of the base oil; di-tert-butyl-p-cresol may vary from 0.1 to 1.0% by weight of the base oil; phenyl-a-naphthylamine may vary from 0.1 to 1% by weight of base oil; dimethylsilicone may vary from 0.0008 to 0.01% by weight of the base oil. The amount of N-acylsarcosines 'in the transmission fluid may vary from 0.10% to .75% based on weight of the compounded fluid, an amount from 0.15 to 0.30% is preferred.

Table I presents data showing the sliding friction properties of compositions of this invention. In the examples the letters A, D, etc. refer to the above-described compositions. The fluids with the additive have been compared with a hydrocarbon oil which is a'mixed base stock having about of solvent refined paraffinic oil of Western origin having a V.I. (Viscosity Index) of 92 and a viscosity of 150 SSU at 100 F. and 80% solvent refined and acid treated oil of Western origin hafing a V1. of about 50 and a viscosity of SOSSU at 100 F. and containing no additives.

method is similar with minor variations to the method described by Haviland et al., Lubrication Engineering, vol. 17, No. 3, pp. 110-117, March 1961. As hereinafter disclosed, the test results correlate with results obtained in standard test transmissions under test driving conditions.

Experience has shown that in an acceptable fluid the coeflicient of friction for each fluid must decrease as the rubbing speed decreases at any given temperature. The coefficient of friction is determined at the velocity and temperature conditions set forth in the table. The coeflicient of friction should not exceed about 0.18 at low rubbing speeds or grabbing and squawk will occur. At the same time the coefficient of friction should be greater than about 0.06 or slipping and flare will occur. It has now been found that the particular N-acylsarcosines have coeflicients of friction above about 0.06. The coeflicients of friction are also below about 0.18. The designation f.-p.m. signifies feet per minute.

The last example shows compounded fluid G to be unacceptable without the N-acylsarcosines of the invention because of the reverse trend of the coefiicient of friction.

The friction properties of the novel fluids are superior to those of hydrocarbon oil by reason of the reverse coeflicients 'of friction at low temperatures. The transmission fluids containing the N-acylsarcosines of the invention possess temperature-volecity-coeflicient of friction variables which are satisfactory for use in automatic transmissions.

The outstanding N-acylsarcosines of this invention were evaluated according to the commercially accepted standard tests which correspond to actual driving conditions encountered on the road. The test procedure was conducted by following the Durability Test'specified by General Motors Corporation, Type A Suflix A Test for automatic transmission fluids. Briefly, according to this procedure a certain model power transmission unit of an Oldsmobile car driven by an Oldsmobile engine is employed. This power transmission unit goes through a maximum throttle acceleration to 4500 r.p.m. and is then allowed to go to idle operating conditions. This cycle is repeated 2400 times. The Squawk or chatter phenomenon is determined by the audible noise and the vibrational characteristics of the power transmission unit. The engine flare is determined by the monitored engine characteristics. During and at the end of the test an acceptable fluid does not exhibit either squawk Table I FRICTIONAL CHARACTERISTICS OF N-OLEYLSAROOSINE Sliding Coeff. of Friction At Example Base Fluid Friction Control Cone, Temp,

Agent Percent F.

Of.p.m. 5f.p.m. 10 f.p.m. 15 I.p.m

0. 181 0. 178 0. 179 0. 174 1 Hydrocarbon- None 176 0. 192 0. 160 0. 160 0. 300 0.230 O. 177 0. 162 0. 158 75 0. 14 0. 166 0. 175 0. 176 2 D N-oleylsarcosine. 0.20 175 0. 09 0. 131 0. 141 0. 14.4 300 0.08 0. 127 0. 128 0. 129 75 0. 15 0.175 0. 182 0. 183 3 F do 0.20 175 0.08 0.130 0. 0. 146 300 0. 12 0. 132 0.132 0. 132 75 0. 210 0. 178 0. 180 0. 175 4 G None 176 0. 178 0. 0. 160 0. 160 300 0. 164 0. 177 0. 162 0. 159

The data in Table I were obtained by taking a piece of the commercial clutch plate facing (a combination of cork and composition paper) and testing it under the temperature velocity conditions in a low load friction apparatus. The apparatus consists of rotating steel disks of the type found in automatic transmissions. The fluid tested surrounds the disk while the clutch facing material is held against the disk by a constant load. This test or flare" phenomenon. According to this test, the compounded fluids with N-acylsarcosines performed outstandingly, meeting all the imposed requirements.

All percentages in the specification and claims are 'by weight. Amounts of the N-acylsarcosine are by'weight of the base fluid, unless otherwise indicated.

I claim:

1. A power'transinission fluid having a viscosity of from about 75 to 1000 SSU at 100 F., consisting essen tially of a major proportion of a mineral lubricating oil base having a viscosity of from 50 to 400 SSU at 100 F. and from 0.10% to 0.75% by weight of N-acylsarcosine of the general formula:

in which R represents an aliphatic hydrocarbon radical containing from 11 to 23 carbon atoms, wherein said mineral lubricating oil base contains (a) from 1.0 to 15% by weight of a polymeric viscosity index improver selected from the group con sisting of (1) mixed oil-soluble polymerized alkyl meth acrylates having an average of 12 carbon atoms in the alkyl chain and a molecular weight of about 220,000, and (2) oil-soluble polyisobutylene having a molecular weight of about 220,000: (b) from 1.0 to 15% by Weight of a polymeric detergent selected from the group consisting of (1) an oil-soluble reaction product of N-methyl piperazine with a quadripolymer comprised of monomeric constituents of dodecyl methacrylate, octadecyl methacrylate, polyethylene glycol methacrylate and glycidyl methacrylate in a molar ratio of about 33/ 17/1/ 1, wherein the polyethylene glycol has a molecular weight of from 500 to 2500 and the molecular Weight of the polymer is from 100,000 to 300,000, and (2) an oil-soluble copolymer of alkyl methacrylate and vinyl pyrrolidone having a molecular weight of about 220,000 having mixed higher alkyl radicals in the alkyl chain;

(c) from 10 to 250 millimoies per kilogram of base oil of calcium petroleum sulfonate having a molecular weight of about 400;

(d) from 0.1 to 1.0% by weight of an oxidation inhibitor selected from the group consisting of phenyl-anapthylamine and di(tertiary butyl)-p-cresol; and

(e) from 0.0008 to 0.01% by weight of a dimethyl silicone polymer foam inhibitor.

2. The power transmission fluid of claim 1, in which the N-acylsarcosine is N-oleylsarcosine.

3. The power transmission fluid of claim 1, in which the polymeric viscosity index improver is a mixed alkyl methacrylate polymer having an average of 12 carbon atoms in the carbon chain and a molecular weight of about 220,000.

4. The power transmission fluid of claim 1, wherein the polymeric detergent is an oil-soluble copolymer of alkyl methacrylate and vinyl pyrrolidone having a molec ular weight of about 220,000 having mixed higher alkyl radicals in the alkyl chain.

5. The power transmission fluid of claim 1, in which the polymeric viscosity index improver is polyisobutylene having a molecular weight of about 220,000.

References Cited in the file of this patent UNITED STATES PATENTS 2,681,891 Bos et al June 22, '1954 2,841,555 Lyons et al. July 1, 1958 2,851,421 Manteuifel et al. Sept. 9, 1958 2,961,404 Francis Nov. 22, 1960 3,042,612 Roebuck et al. July 3, 1962 3,112,232 Early et al. Nov. 26, 1963 FOREIGN PATENTS 856,773 Germany Nov. 24, 1952 

1. A POWER TRANSMISSION FLUID HAVING A VISCOSITY OF FROM ABOUT 75 TO 1000 SSU AT 100*F., CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF A MINERAL LUBRICATING OIL BASE HAVING A VISCOSITY OF FROM 50 TO 400 SSU AT 100*F. AND FROM 0.10% TO 0.75% BY WEIGHT OF N-ACYLSARCOSINE OF THE GENERAL FORMULA: 